Geometrical sketching template



Nov. 8, 1949 A. J. ROPER GEOMETRICAL SKETCHING TEMPLATE Filed NOV. 13,1945 INVENTOR AUSTIN JOHN ROPER ATTORNEY Patented Nov. 8, 1949GEOMETRICAL SKETCHING TEMPLATE Austin John Roper, Vancouver, BritishColumbia,

Cana

Application November 13, 1945, Serial No. 628,245

- In Canada November 21, 1944 I 1 Claim. 1

My invention relates to improvements in a geometrical sketching templateand consists in forming a template preferably of Celluloid ortransparent plastic material and forming or cutting the edges thereofinto lore-determined configurations and further cutting or forming inthe body proper thereof, a plurality of pre-determined geometricalfigures.

The object of my invention is, to provide a simple, useful and accuratetemplate as an aid to engineering students and professional men insketching graphically, the problems and the solution of such problems inengineering design, particularly that branch known as thermo-dynamics,but which may also be used by draftsmen in various other branches ofengineering as a drafting tool.

Heretofore, students and engineers have had, of necessity, to dofreehand sketching, which in the majority of cases, is poorly executed;or have recourse, as an alternative, to numerous conventional aids suchas so called French curves which are cumbersome and require carefulmanipulation to obtain the desired results.

Students, particularly, have been known to use coins, buttons, paperclips and such devices in an effort to prepare neat notes andcommendable examination papers, with a resultant loss of valuable time.

Wherefore, it had been my endeavour to provide a single device in thenature of a template that will adequately fill such a need, and I attainthis object by means of the device illustrated in the accompanyingdrawings and specification following, in which:

Referring to the drawings:

Fig. l is a plan of the template, and Fig. 2 a side view of the same.

Similar numerals refer to similar parts throughout.

In the drawings the numeral I represents the template proper, formedpreferably of Celluloid or transparent plastic material, having cut orformed on one edge thereof, a series of fingerlike configurations l, 2and 3 of definite shape conforming to sine waves of certain knownformulae having to do with voltage, current and power variations ininductive circuits in which the curve or wave as shown but the numeral ltakes the form based on the formula A sin wt; 2 a

the form of A sin Zwt and 3 the form B sin wt wherein a: is equal to twotimes 11' times frequency, with 15 indicating the time factor. Inpreparing notes it is often necessary to superimpose one form of waveupon another form of wave whose points of origin coincide with theorigin of a single set of co-ordinates representing time and amplitude;and if executed freehand or with curves of wrong profile, theillustration becomes confused and presents the appearance of a mass ofunbalanced waves intermingling without proportion.

Adjacent one side of each of the curves or waves so described, shoulders4, are provided as a means to indicate the origin of coordinates inrespect to positive and negative amplitude.

Extending around one of the corners of the template, a further curve 5,is provided, which is related to definite formulae based on pressure andvolume in thermo-dynamics, usually expressed by the term PV =C in whichpressure multiplied by volume, whose result, when raised some selectedpower k, equals some constant Along one edge and around said pressurevolume curve a circular scale, calibrated in degrees is provided forconvenience of plotting angularity of lines.

The remaining edge, 6, of the template, constitutes a straight edge forruling lines and has stamped or impressed thereon. a measuring scalecalibrated in inches and tenths of an inch, but which may be of anyother suitable scale, as a further convenience, and while suchcalibrations for straight and circular measurements are conventional,they nevertheless become necessary in plotting graphs and have theadvantage of dispensing with additional instruments.

Adjacent the calibrated straight edge, 6, and parallel thereto, two rowsof perforations l and 8 are provided for the purpose of determiningareas by the mid-ordinate method and in which the scale of interval ofthe row indicated by the numerals l is greater than the scale intervalof the rod indicated by the numerals 8. It will be noted that there aretwelve perforations in each row, but that only ten of the perforationsof each row are equally spaced and, significantly, that the first andtwelfth perforation of each row, counting either way, lie a distancefrom the second and eleventh perforations, equal to one-half anysucceeding interval of the ten equally spaced perforations. The objectof this scale is to dispense with the employment of a polar planimeter,which is an expensive and unwieldy instrument, particularly forstudents, and requires careful manipulation.

In using the mid-ordinate scale, the second, eleventh and interveningperforations become the Which the numerals 9, [0, ll, l2, l3 and I4indi-.

cate circles of grades diameter which may be used for drawing simplecircles, concentric circles, eccentric, and the like, cylinders, pulleydiagrams and graphical expression of polar moments of inertia, andgenerally, any diagrams which usually require the use of a spring bow.

The numeral I5 indicates an aperture which may be used to illustratestructural shapes in cross section as I beams, H beams, channels, angleiron and T shapes for the purposes of indicating their respectivedimensions or illustrating the elements of such sections.

16 indicates a rectangular opening which may be used for drawing rightangles, triangles, squares and like figures or indexing notes; and IT, aslot for indexing or enclosing the answer to a problem; which is theusual practice in preparing engineering notes and examination papers,where it is desirable to indicate such answers apart from the maze ofdetailed calculations.

I am aware that prior to my invention templates for drawing curves ofvarious shapes in the form of simple, compound, spiral, sine andinvolute have been made. I therefore do not claim such a combinationbroadly; but

I claim:

In a geometrical sketching template, of a Celluloid or transparentplastic nature, the combination of a series of sine wave forms inprofile, disposed along an edge thereof of said template, said wavescomprising curves formed in varying frequencies alternating throughpositive and negative amplitude, shoulders adjacent said waves, and saidshoulders disposed upon and along the frequency ordinate of said wavesin relation to and at an amplitude ordinate of said waves, as a means todifferentiate between positive and negative amplitude.

AUSTIN JOHN ROPER.

REFERENCES CITED The following references are of record in the file Ofthis patent:

UNITED STATES PATENTS N mbe Name Date vD. 136,395 Deckman Sept. 21, 19431,582,185 Moeckel Apr. 27, 1926 1,650,269 Haederer Nov. 22, 19271,989,223 Barr Jan. 29, 1935 I 2,960,686 Niemic Nov. 10, 1936 2,371,485Waldman Mar. 13, 1945 FOREIGN PATENTS Number Country Date 282,686 GreatBritain 1 Aug, 23, 1928

